I still use the old method I learned from my father who learned it from his....
About every 4th tankfull I will go the Super and add a bottle of injector cleaner. I average 21 to 23 MPG with my VX, which is way above normal for city/highway driving. I just completed a 405 mile round trip to Brookline, MA from my house in Mt. Tabor, VT and I still had about 3 gallons in the tank when I refueled. Maybe I just got lucky with my 3.5
John